Essential component parts of a gas turbine include a compressor, a turbine with rotor blades and at least one combustion chamber. The rotor blades of the turbine are arranged as rotor blade rings on a shaft which in the main extends through the entire gas turbine, and is connected to a consumer load, for instance a generator for power generation. The shaft provided with the rotor blades is also called a (turbine) rotor. Between the rotor blade rings are guide vane rings, which act as nozzles to conduct the working medium through the turbine.
During operation of the gas turbine compressed air from the compressor is fed to the combustion chamber. The compressed air is mixed with a fuel, for example oil or gas, and the mixture is combusted in the combustion chamber. The hot combustion exhaust gases are eventually fed to the turbine as a working medium via a combustion chamber outlet, where they expand and cool and transfer pulse to the rotor blades, and thus perform work. The guide vanes are in this case used to optimize the transmission of pulse.
A typical burner arrangement for gas turbines, as described in U.S. Pat. No. 6,082,111 and as is used in particular in so-called pipe combustion chambers, generally has an annular support with a number of fuel nozzles distributed evenly around the circumference of the ring. Fuel nozzle openings are arranged in these fuel nozzles, with which fuel can be injected into an air inlet channel. The fuel nozzles represent a main stage of the burner, which serves to generate a premixed flame, in other words a flame in which the air and the fuel are mixed before ignition. To minimize the formation of NOx in the flame, premix burners are operated with lean air-fuel mixtures, in other words with mixtures which contain relatively little fuel.
Through the center of the annular fuel distribution ring typically extends a pilot burner, which is embodied as a diffusion burner, i.e. it generates a flame in which the fuel is injected directly into the flame, without first being mixed with air. Apart from starting up the gas turbine, the pilot burner also serves to stabilize the premixed flame, which to minimize the emission of pollutants is frequently operated in a range of the air-fuel ratio which without an auxiliary pilot flame could result in flame instabilities.
A burner arrangement such as the described burner arrangement typically has a number of fuel nozzles machined out of a metal block and welded to the support for feeding fuel to the combustion chamber. The support in this case distributes the fuel to the individual nozzles through built-in fuel passages.
To be able to provide enough space for machining the fuel passages, the support blank and thus the subsequent support must be of a certain minimum thickness. This increases the weight of the burner arrangement as well as the material costs. Machining in the fuel passages is also a labor-intensive process.